how to control beaglebone gpio pins

Question

I'm trying to make a program for beaglebone to let me control the gpio pins. I tried to use sprintf() but doesn't accept input as I know.

I have to re-write couple files in the beaglebone like

gpio export active the pin gpio gpio$pin/direction pin mode in/out gpio gpio$pin/value pin value 1/0

guys..!! just need a idea how to accomplish my goal.

I'm newbie in c++. any information or comment I'll appreciated thks guys for your time.

"*I'm trying to make a program for beaglebone ...*" -- You've only specified the HW platform and nothing about the target software environment or OS. It's not like you are required to only run Linux on a BB. — sawdust, Oct 19 '22 at 00:43

Brian · Answer 1 · 2014-01-18T02:52:51.057

Here is a tutorial on using c++ to control the LEDs: http://derekmolloy.ie/beaglebone-controlling-the-on-board-leds-using-c/

Halfway down the page is the C++ code. Take this implementation, but instead of writing to the LED device files, write the appropriate information to the GPIO device files, like in this manual:

http://elinux.org/images/3/33/GPIO_Programming_on_the_Beaglebone.pdf

#include<iostream>
#include<fstream>
#include<string>
using namespace std;

int main(){
   std::fstream fs;

   fs.open("/sys/kernel/debug/omap_mux/gpmc_ad4");
   fs << "7";
   fs.close();
   fs.open("/sys/class/gpio/export");
   fs << "32";
   fs.close();
   fs.open("/sys/class/gpio/gpio32/direction");
   fs << "out";
   fs.close();
   fs.open("/sys/class/gpio/gpio32/value");
   fs << "1"; // "0" for off
   fs.close();
   // select whether it is on, off or flash

   return 0;
}

As per [here](https://e2e.ti.com/support/processors/f/791/t/270719), current version of Beaglebone Black do not use `omap_mux`. This instruction will not work for newer BBBs — Rufus, Oct 29 '18 at 08:56
Refer to [this question](https://stackoverflow.com/questions/16872763/configuring-pins-mode-beaglebone) for configuring pin modes — Rufus, Oct 29 '18 at 09:41

score 0 · Answer 2 · answered Oct 18 '22 at 04:05

An enhanced version uses Cpp and is available in chapter 6 of Derek Molloy's book. Read from page 214:

~/derek/chp06/GPIO$ cat simple.cpp 
/* A Simple GPIO application
* Written by Derek Molloy for the book "Exploring BeagleBone: Tools and
* Techniques for Building with Embedded Linux" by John Wiley & Sons, 2018
* ISBN 9781119533160. Please see the file README.md in the repository root
* directory for copyright and GNU GPLv3 license information.            */

#include<iostream>
#include<unistd.h> //for usleep
#include"GPIO.h"
using namespace exploringBB;
using namespace std;

int main(){
   GPIO outGPIO(44), inGPIO(45);

   // Basic Output - Flash the LED 10 times, once per second
   outGPIO.setDirection(OUTPUT);
   //for (int i=0; i<10; i++)
  while(1){
      outGPIO.setValue(HIGH);
      usleep(1000); //micro-second sleep 0.5 seconds
      outGPIO.setValue(LOW);
      usleep(1000);
   }
   // Basic Input example
   inGPIO.setDirection(INPUT);
   cout << "The value of the input is: "<< inGPIO.getValue() << endl;

   // Fast write to GPIO 1 million times
   outGPIO.streamOpen();
   for (int i=0; i<1000000; i++){
      outGPIO.streamWrite(HIGH);
      outGPIO.streamWrite(LOW);
   }
   outGPIO.streamClose();

   return 0;
}

Compile and run as

∼/exploringbb/chp06/GPIO$ sudo ./simple

how to control beaglebone gpio pins

2 Answers2